Illuminated displays, such as for advertising, scorekeeping and other message and signal indication are well known. Such illuminated displays have been found very effective in attracting and maintaining the attention of an observer and delivering a message or other information. Conventional illuminated displays usually consist of a plurality of incandescent lamps in the form of separate light bulbs, which are mounted in a matrix arrangement on a display board. Each bulb forms a particular pixel in the illuminated display. An optical control system is used which causes the bulbs to be individually energized and de-energized in a predetermined manner to simulate alpha-numeric characters or other graphics.
One of the principal disadvantages in such displays which use a separate incandescent lamp for each of the pixels is the considerable number of lamps required, along with a very sizable power requirement to produce an illuminated display of sufficient intensity for legibility at a distance. Such displays using incandescent lamps have further proven to be expensive to operate and maintain, and also do not perform well either in a continuous or in a pulsed application. This is because the filament of the lamp requires time to heat-up to incandescence when turned on as well as to cool down after being turned off. There is also a possibility that, as a consequence of lamp failure, the signal desired to be indicated will be misinterpreted or garbled.
Light-transmitting fibers or cables have also been used in illuminated displays. For example, it is known to illuminate lenses arranged in a display matrix through the use of light conducting optical fibers. The elongated optical fibers are typically arranged at one end into a light conductor bundle with the bundled ends of the optical fibers illuminated by a lamp. The other end of each cable terminates in a lens of the display. When the bundle is illuminated, the lenses associated with that bundle are also illuminated. Such optical fiber systems are shown in U.S. Pat. No. 4,113,347, and U.K. Pat. No. 2,051,447.
These optical fiber display systems of the prior art ordinarily use a separate bundle which is illuminated by its own incandescent lamp to form a particular character or other graphic on the display. That is, a separate bundle and lamp is required for each character or graphic desired.
One drawback of such a system is that the number of characters which can be generated is limited due to the increase in the number of bundles and lamps required for each additional character. There is also some difficulty in efficiently attaching the numerous ends of the optical fibers making up each of the individual bundles to the lenses of the display face. That is, a single lens in the display may have a plurality of optical fibers connected to it. Some of these fibers will be located off-axis on the lens, which can reduce the intensity of the light from the lens. The power consumption of each of the lamps used to illuminate the bundles, while less than that of a display using incandescent lamps as the pixels, is still sizable.
It will be noted in U.S. Pat. No. 3,962,702 at FIG. 5 that a mechanism is shown whereby adjacent bundle ends may be shuttered and illuminated by a single lamp. This may reduce the number of lamps required, but still has the significant disadvantage of requiring a separate bundle for each of the characters to be shown in the display. Many lamps would still be required in order to provide adequate illumination for a large number of bundles with the type of shutter arrangement indicated in the '702 patent.
An alternative to the use of separate bundles of optical fibers for each of the characters to be displayed is the use of a plurality of prearranged groups of optical fibers which can be illuminated in certain combinations to make each alphanumeric character. This is done through the use of an apertured light mask interposed between a lamp and the groups of fiber ends. Such systems are shown in U.S. Pat. Nos. 3,836,991 and 3,948,209, for example. In these systems, the mask registers specific apertures with selected groups of fibers to thereby produce a particular character on the display face. Although a single source of illumination can be used in this system, the types of characters that can be made are limited by the number of fiber groups as well as the apertures provided in the mask. Use of a rotary mask further requires considerable time in moving from one alphanumeric character to another, whether done manually or through a mechanical drive.
A problem to be solved by any optical fiber display is that of providing sufficient light intensity for the pixels of the illuminated display, particularly a large outdoor display which is to be seen from a distance in daylight, such as in roadside sign applications, athletic stadium scoreboards, etc. Part of that illumination problem is to enable the display to be read from a broad range of viewable angles, and not just from a head-on approach.
For the most part, these light intensity considerations coupled with the limited character generating ability and slow character-change response time of existing optical fiber illumination mechanisms have particularly inhibited the construction of fairly large optical fiber displays which can be seen at long distances.